I eat lunch _____________ 12: 00 noon.[ ]
A. on
B. in
C. at
答案:C
常用“OT”试验皮试液的浓度是()
A.1:100
B.1:200
C.1:1000
D.1:2000
E.1:10000
对于可视电话业务,一般其下行带宽在()左右。